A piezoelectric/electrostrictive actuator has an advantage of being capable of precisely controlling displacement in a submicron order. Especially, a piezoelectric/electrostrictive actuator using a sintered body of a piezoelectric/electrostrictive porcelain composition as piezoelectric/electrostrictive body has advantages of high electromechanical conversion efficiency, large generative force, high-speed response, high durability, and low power consumption, in addition to the advantage of being capable of precisely controlling displacement. Drawing on these advantages, the piezoelectric/electrostrictive porcelain actuator has been adopted to a head of ink jet printer and an injector of a diesel engine.
As the piezoelectric/electrostrictive porcelain composition for the piezoelectric/electrostrictive actuator, a Pb (Zr, Ti)O3(PZT) based composition has hitherto been used. However, since an influence exerted by elution of lead from the sintered body on global environment has become a deep concern, a (Li, Na, K)(Nb, Ta)O3 based composition has also been considered. It is however noted that there are many cases where the (Li, Na, K)(Nb, Ta)O3 piezoelectric/electrostrictive porcelain composition is used with a Mn compound added thereto since performing a poling process on the composition as it is difficult.
For example, Japanese Patent Application Laid-Open No. 2004-244302 discloses a piezoelectric/electrostrictive porcelain composition represented by a general formula: {Lix(K1-yNay)1-x}(Nb1-z-wTazSbw)O3 which was obtained by adding a Mn compound to a perovskite type oxide.
However, the (Li, Na, K)(Nb, Ta)O3 based piezoelectric/electrostrictive porcelain composition easily becomes hardened by addition of the Mn compound, and there has thus been a problem in that electric field induced strain, which occurs at the time of applying a high electric field and is of importance for the piezoelectric/electrostrictive actuator, decreases due to addition of the Mn compound.